Smoking product of cellulosic material subjected to a nitrogen dioxide oxidation and a mild oxidation with peroxide

ABSTRACT

The preparation of a smoking product formulated of a cellulosic material which has been oxidized in the presence of nitrogen dioxide and in which the oxidized product is subjected to a second mild oxidation reaction with a dilute peroxide solution, with or without previous reduction with borohydride.

United States Patent Inventors Theodore S. Briskin;

Geoffrey R. Ward, Beverly Hills, Calif. 745,402

July 17, 1968 Apr. 20, 1971 Sutton Research Corporation Los Angeles, Calif.

Continuation-impart of application Ser. No. 595,622, Nov. 21, 1966, Continuation-inpart of application Ser. No. 674,994, Oct. 12, 1967.

Appl. No. Filed Patented Assignee U.S.Cl 131/2, 131/17, 131/140, 260/212 [50] Field ofSearch 131/2, 15, 17, 140-144; 260/212 [56] References Cited UNITED STATES PATENTS 3,364,200 1/1968 Ashton et a1 260/212 FOREIGN PATENTS 702,918 2/1965 Canada 131/2 Primary Examiner-Me1vin D. Rein AtmrneyMcDougall, Hersh, Scott & Ladd ABSTRACT: The preparation of a smoking product formulated of a cellulosic material which has been oxidized in the presence of nitrogen dioxide and in which the oxidized product is subjected to a second mild oxidation reaction with a dilute peroxide solution, with or without previous reduction with borohydride.

SMOKING PIIOIIIJC'I OI CELLIIIJOSIC MATERIAL SUBJEC'IIED TO A NITROGEN DIOXIDE OXIDATION AND A MILD OXIDATION WI'III PEIIOXIDE This is a continuation-in-part of our copending applications Ser. No. 595,622, filed Nov. 2i, l966, and entitled Smoking.

Products," and Ser. No. 674,994, filed Oct. 12, l967, and entitled Smoking Products and Process for Making Such Products."

As used herein, the term smoking products" is meant to refer to and to include filler material embodied in cigarettes, cigars and for use with pipes and the like,and mixtures thereof with various proportions of tobacco and including cigarette papers and wrappers used in the preparation of such cigars and cigarettes, and it includes cigarettes, cigars and the like products manufactured with such filler materials and wrappers.

In the aforementioned copending applications, description is made of the preparation of a smoking product suitable for use in cigarettes, cigars or with pipes wherein the smoking product is prepared of relatively pure cellulosic materials subjected to selective oxidation with liquid nitrogen dioxide to convert preferably more than 90 percent of the methylol groups in the cellulosic molecule to yield a product which can be referred to as an oxycellulose or polyuronic acid. The oxidation reaction product is further processed by removal of liquid nitrogen dioxide by vaporization and preferably by washing the oxidized cellulosic product with water and/or alcohol and/or acetone or other solvent for removal of solubiliaed foreign material, including oils, waxes, latices and the like, which contribute undesirably to the taste and aroma when used as a smoking product in accordance with the practice of this invention.

As further described in the aforementioned copending applications, the oxidized and cleansed cellulosic derivative is further processed by a reduction reaction with borohydrides of an alkali or alkaline earth metal such as sodium or lithium borohydride for reduction of such nitrogen compounds, quinones, ketones, aldehydes and unsaturates as otherwise have a tendency to impart undesirable aroma and taste as the smoking product is burned. The product before or after reduction can be subjected to additional oxidation with a dilute peroxide solution as a means for eliminating further groupings which impart undesirable aroma or taste to the product.

The resulting smoking product is then formulated with mineralizing agents such as oxalates, glycolates, diglycolates, lactates, pivalates or tannates of such metals as calcium, magnesium, lithium, potassium, barium or strontium, preferably introduced to form the salt internally in the cellulosic derivative for purposes of providing desired ashing characteristics. Instead of forming the described salts internally in the cellulosic derivative, limited beneficial characteristics can be achieved by external application of such mineralizing agents. As described, the desired internal introduction is achieved by first wetting the cellulosic derivative with metal cation in dilute solution for absorption into the cellulosic derivative followed by exposure to the acid anion in solution to precipitate the metal salt in situ in the cellulosic material.

The treated cellulosic derivatives can be further processed to improve the burning, glow and smoking characteristics by formulation to include a potassium salt, such as potassium oxalate or by the addition of rubidium or cesium in the form of compounds thereof in amounts within the range of 0.1 percent to percent by weight but preferably less than l percent by weight, as described in the copending application Ser. No. 623,528, filed Mar. 16, I967, and entitled Smoking Products and Process for Their Manufacture." Smoke generators for improving the appearance of the smoke generated by the product can be introduced as by the introduction of various fatty acids, esters, ethers and the like and the aroma and pH characteristics can be achieved by the addition of volatilizable alkalyzing material such as ammonium oxalate and the like.

The resulting product is suitable for use as a smoking product alone or in admixture with tobacco to produce a smoking product having good taste, good aroma and good appearance.

As the cellulosic raw material, use can be made of various forms of cellulose, such as wood pulp, alpha-cellulose, flax, fibrous carbohydrates, seaweed carbohydrates, bamboo filaments, cotton filaments, hemp, straw, refined paper, rice paper, filamentous gums and even plants and plant leaves and the like fibrous materials from which noncarbohydrate components have been separated, all of which is hereinafter referred to as cellulosic material.

lt is preferred to make use of a purified cellulosic material from which various of the sugars, proteins, chlorophylls, flavones, colors, lignins, oils, waxes, resins and latices have been removed since these contribute undesirable odors and tastes to the smoking product.

Purified cellulose is unsatisfactory for use as a smoking product from the standpoint of taste, aroma and burning characteristics. This is believed to stem from the acids and aldehydes that are evolved upon pyrolysis of the cellulose. It has been found that many of the defects of pure cellulose can be greatly alleviated by conversion of the methylol groups to carboxyl groups to produce a product which readily pyrolyzes with complete burning of the cellulosic molecule into water vapor, and oxidation products of carbon such as carbon dioxide and low molecular weight compounds which readily volatilize off. Thus the object is to achieve'selective oxidation of the cellulosic material to convert methylol groups, primarily the methylol groups containing the C carbon, to carboxyl groups, preferably with better than percent conversion. There is no objection to further oxidation beyond I00 percent by conversion of secondary hydroxyl groups as on C and C to monoand diketo groups so long as cleavage does not occur.

lt has been found that liquid nitrogen dioxide yields an oxidation reaction that has the desired selectivity and that complete wetting of the cellulosic materials can be achieved almost instantaneously with liquid nitrogen dioxide with the result that the oxidation reaction takes place substantially uniformly throughout the cross section of the cellulosic material and at a much more rapid rate whereby a more uniformly and more completely oxidized product is obtained in less time. Furthermore, liquid nitrogen dioxide, when used in the proportions most suitable for the practice of this invention, operates as a quench immediately to dissipate heat generated by the exothermic reaction so as to avoid the formation of hot spots or nonuniformity in the reactions.

It has been found that the course of the oxidation reaction and the treatment of the oxidized cellulosic material can be influenced by a number of very important factors which cannot be translated into reactions with gaseous nitrogen dioxide but which can be employed in the oxidation of the cellulosic material with liquid nitrogen dioxide thereby greatly to enhance the oxidation process including increase in reaction rate, increase in the amount of conversion, uniformity of oxidation, as well as ease of purification and subsequent treatment of the oxidized reaction product, as will hereinafter appear.

In our copending application Ser. No. 745,221, filed concurrently herewith and entitled A smoking Product and Method of Preparation," description is made of the oxidation of a cellulosic material by suspension in liquid nitrogen dioxide in the ratio of 1 part by weight cellulosic material to 5 to l000 parts by weight liquid nitrogen dioxide and preferably 1 part by weight cellulosic material to 25 to 50 parts by weight of liquid nitrogen dioxide. The reaction therein is carried out at a temperature within the range of 15 to 65 C. and at an autogenous pressure when the reaction temperature exceeds 21 C. (the boiling point of nitrogen dioxide, N 0,).

ln our copending application Ser. No. 745,135, filed concurrently herewith and entitled Preparation of Smoking Product of Cellulose Derivatives and Process, description is made of the selective oxidation of cellulosic material wherein the oxidation reaction, including reaction rate and the amount of conversion, is materially improved by formulation of the oxidation reaction medium to contain up to 8 percent by weight of water in the liquid nitrogen dioxide system and by carrying out the reaction at elevated temperature above 15 C. and preferably within the range of 20 to 45 C., depending somewhat upon the amount of moisture present in the reaction medium, whereby the reaction medium is rendered relatively nonelectrically conductive so that the presence of water in the reaction medium will not result in attack or degradation of the cellulosic material to be oxidized and wherein the formulation to include aqueous medium in the reaction of liquid nitrogen dioxide operates also to adjust the specific gravity of the reaction medium in the direction towards the specific gravity of the cellulosic material whereby suspension of the cellulosic material in the reaction medium is easier to achieve and maintain. The result is a more rapid and uniform oxidation reaction of the cellulosic material to produce a better product at a more rapid rate.

In our further copending application, Ser. No. 745,134 filed concurrently herewith, and entitled "Cellulosic Smoking Product and Method in the Preparation of Same," description is made of the process for selective oxidation of cellulosic material with liquid nitrogen dioxide, with or without up to 8 percent by weight of water, wherein oxygen or an oxygen containing gas is introduced during the oxidation reaction in amounts corresponding to l to 50 parts by weight of oxygen per part by weight of celluloisic material. The introduction of oxygen, during the selective oxidation reaction with nitrogen dioxide, operates to reconvert nitrous acid and nitric oxide to nitrogen dioxide and to accelerate the oxidation reaction.

In our still further copending application Ser. No. 745,132, filed concurrently herewith and entitled Method for Preparation of Smoking Product with Selective Reduction following Selective Oxidation," description is made of the treatment of the cellulosic material, after oxidation with nitrogen dioxide, wherein the oxidized cellulosic material is subjected to a reduction with an alkali metal or alkaline earth metal borohydride or with nascent hydrogen to effect reduction of nitro or nitric acid groups to corresponding amino groups and to effect reduction of quinone, ketone or aldehyde groups and unsaturates. For this purpose, the oxidized cellulosic material is reacted with l to 1000 times its weight of an aqueous solution containing 0.5 percent to 5 percent by weight borohydride at a pH below 7 but above 3, and preferably a pH within the range of 6 to 6.5, and at a temperature preferably within the range of to 30 C.

lt has been found that the odor emitted during burning of the smoking product, as in a cigarette, cigar or pipe, is further improved by subjecting the cellulosic material, after selective oxidation with liquid nitrogen dioxide, to a further oxidation reaction with a very dilute solution of peroxide. It appears that the peroxide attacks odor generating groups that either escape the oxidation reaction with liquid nitrogen dioxide or are not attacked during selective oxidation with nitrogen dioxide. Whatever the reason, when the cellulosic material, oxidized with liquid nitrogen dioxide, is subjected to a mild treatment with peroxide, such as hydrogen peroxide, a noticeable improvement is experienced in the odor characteristics of the resulting product when smoked since otherwise undesirable odors become evident even when only small amounts of impurities, ranging from traces to 0.5 percent by weight, are present.

When a borohydride reduction reaction is employed, as described in the aforementioned copending application filed concurrently herewith, after the oxidation with liquid nitrogen dioxide, the mild oxidation treatment with peroxide, in accordance with the practice of this invention, can be carried out before or after the borohydride reduction. When employed after the reduction reaction, the mild peroxide oxidation of this invention serves to oxidize amines formed by the borohydride reduction and not removed by the subsequent wash. Such amines are objectionable in the smoking product, particularly when present in the form of an aromatic amine as from nitrolignin and other nitro aromatic compounds. The peroxide effects oxidation of amino groups to corresponding alcohol or aldehyde groups.

Use cannot be made of peroxides formed of heavy metals or which have groupings that introduce other undesirable odors into the cellulosic material. On this subject, it is undesirable, for example, to make use of benzoyl peroxide, tertiary butyl peroxide or other peroxide containing aromatic or long chain alkyl or substituted alkyl groups, but use can be made of alkali metal peroxides and preferably hydrogen peroxide as the oxidizing agent.

Use can be made of an aqueous solution of hydrogen peroxide or alkali metal peroxide present in solution in an amount within the range of 0.001 percent to 1 percent by weight and preferably within the range of 0.02 percent to 0.2 percent by weight of the reaction medium. The treating solution should be adjusted to a pH within the range of 4 to 6.5 and preferably within the range of 4 to 4.5, and the reaction should be carried out at a temperature within the range of 0 to 50 C. and preferably within the range of ambient temperature to 30 C. When use is made of a solution having a pH below 4, problems are raised from the standpoint of hydrolysis of the oxidized cellulosic material. With a solution having a pH above 6.5, there is a tendency to form polyuronic anions with corresponding increase in solubilization of the derivative. At temperatures above 50 C., there is a tendency for the materials to dissociate. Temperatures within the lower portion of the range are preferred for the reason that mercerization can take place to cause swelling of the cellulosic material for better penetration of the reactants.

The time of reaction is not pertinent. One minute of exposure has a very desirable effect and, while the reaction can be continued for more than 60 minutes, such longer residence times are undesirable from a practical or commercial standpoint. In the preferred practice of this invention, a reaction time within the range of 5 to 20 minutes is recommended.

While not equivalent to the peroxides, the type of oxidation achieved by the use of peroxides can be secured by the use of ozone blown through a water suspension of the cellulosic material or by otherwise exposing the wet cellulosic material to ozone containing gases.

It is also possible to combine the peroxide treatment with liquid nitrogen dioxide oxidation by formulating the liquid medium of liquid nitrogen dioxide, preferably with water added, to contain a small amount of hydrogen peroxide within the range described.

Having described the basic concepts of this invention, examples will now be given by way of illustration, but not by way of limitation, of the practice of this invention.

EXAMPLE 1 A highly purified commercial grade of paper fonned of wood pulp is cut into strands of about 2 mm. in width and immersed in approximately 100 times its weight in liquid nitrogen dioxide. The oxidation reaction in liquid nitrogen dioxide is continued for 7 to 8 days while maintaining the medium at a temperature of about 20 C. When the oxidation reaction has been completed, as indicated by the conversion of at least percent of the methylol groups on the C position of the cellulosic molecule, oxidation is discontinued by draining the liquid nitrogen dioxide from the oxidized cellulosic material. The oxidized product is then washed with water to remove water solubles.

The oxidized cellulosic material is then immersed in twenty times its weight of an aqueous solution containing 0.02 percent by weight hydrogen peroxide with the solution adjusted to a pH of 4. Reaction is continued at ambient temperature for 20 minutes after which the liquid oxidizing medium is drawn off and the resulting oxidized cellulosic material is washed with water and dried.

EXAMPLE 2 A highly purified wood pulp is loaded into a reactor with liquid nitrogen dioxide in the ratio of 1 part by weight of pulp to parts by weight of liquid nitrogen dioxide. The reaction medium is maintained at 20 C. and air is blown through the reaction medium during the reaction period which is continued for about 6 to 7 days. Upon completion of the oxidation reaction with liquid nitrogen dioxide, the liquid reactant is drained from the oxidized cellulosic material and the cellulosic material is washed first with anhydrous liquid nitrogen dioxide and then with water to remove water solubles.

The oxidized cellulosic material is then subjected to a reduction reaction with an alkali metal borohydride such as sodium borohydride present in the aqueous medium in an amount of 0.5 percent by weight at 20 C. and at a pH of 6.5 to 7. Treatment is continued for 20 minutes and the resulting product is washed and dried. The dry product is then immersed in times its weight of an aqueous solution containing 0.05 percent by weight hydrogen peroxide at a pH of 4.5.Reaction at 20 C. is continued for 20 minutes and then the resulting product is washed and dried.

EXAMPLE 3 A purified wood pulp is subjected to a selective oxidation reaction by introduction into a pressure vessel with 100 times its weight of liquid nitrogen dioxide containing 1.5 percent by weight of water and 0.02 percent by weight of hydrogen peroxide. The oxidation reaction with liquid nitrogen dioxide and with a small amount of hydrogen peroxide is carried out at 30 C. for 24 hours. After oxidation is completed, the liquid reactants are withdrawn from the oxidized cellulosic material and the latter is warmed and evacuated to drive off the volatilizable gases and then it is washed with water to remove water solubles.

EXAMPLE 4 The oxidized cellulosic material of Examples 1 or 2 is immersed in water free of heavy metal ions and ozone is bubbled through the liquid medium for 30 minutes to effect selective oxidation of the oxidized cellulosic material. The water is drained from the resulting product and the oxidized cellulosic material is dried.

The products resulting from Examples 1 to 4 will be found to have improved smoking characteristics from the standpoint of taste and aroma, as compared to the cellulosic material prior to the described selective oxidation treatments. However. it is preferred further to process the oxidized cellulosic materials, as described in the aforementioned eopending applications, to efiect modifications by the introduction of one or more agents such as mineralizing and ashing agents, represented by calcium oxalate; smokegenerating agents; neutralizing agents such as ammonium oxalate; an amine oxalate salt; agents for controlling glow and burning rate, such as salts of potassium, cesium or rubidium,

and agents for controlling color.

Description has been made of the treatment of cellulosic material for improving the smoking characteristics for use thereof as a smoking product by selective oxidations including a liquid nitrogen dioxide oxidation and a mild hydrogen peroxide oxidation whereby various of the objectionable groupings originally present in the cellulosic material are converted to groupings which permit easy elimination from the smoking product or else are not found to be objectionable in the product when smoked.

It will be understood that changes may be made in the details of formulation and operation without departing from the spirit of the invention.

We claim:

1. In the process for preparing a smoking product from cellulosic material in which the cellulosic material has previously been oxidized with nitrogen dioxide, the steps of sub ecting the oxidized cellulosic material to a subsequent mild oxidation by admixture with a dilute solution of a peroxide selected from the group consisting of hydrogen peroxide and alkali metal peroxides at a pH within the range of 4 to 6.5 and at a temperature below 50 C.

2. The process as claimed in claim 1 in which the reaction is carried out with the peroxide solution at a pH within the range of 4 to 4.5. i

3. The process as claimed in claim 1 in which the peroxide is present in the solution in an amount within the range of 0.001 percent to 1 percent by weight.

4. The process as claimed in claim 1 in which the peroxide is present in the solution in an amount within the range of 0.002 percent to 0.2 percent by weight.

5. The process as claimed in claim 1 in which the peroxide is hydrogen peroxide.

6. The process as claimed in claim 1 in which the aqueous solution contains an alcohol to prevent solubilization of the oxidized cellulose.

7. The process as claimed in claim 1 which includes the step of subjecting the oxidized cellulosic material to a reduction reaction prior to the mild oxidation step.

8. The process as claimed in claim 7 in which the reduction reaction is carried out in the presence of a borohydride selected from the group consisting of an alkali metal borohydride and an alkaline earth metal borohydride.

9. The process as claimed in claim 7 in which the reduction is carried out in the presence of nascent hydrogen.

10. In the process for preparing a smoking product from cellulosic material in which the cellulosic material has previously been oxidized with nitrogen dioxide, the step of subjecting the oxidized cellulose to a mild oxidation by wetting the oxidized cellulosic material with aqueous medium and exposing the wet oxidized cellulosic material to ozone.

11. A smoking product formed of cellulosic material oxidized with nitrogen dioxide and subjected to a subsequent mild oxidation. with a peroxide selected from the group consisting of hydrogen peroxide and an alkali metal peroxide, as described in claim 1. 

2. The process as claimed in claim 1 in which the reaction is carried out with the peroxide solution at a pH within the range of 4 to 4.5.
 3. The process as claimed in claim 1 in which the peroxide is present in the solution in an amount within the range of 0.001 percent to 1 percent by weight.
 4. The process as claimed in claim 1 in which the peroxide is present in the solution in an amount within the range of 0.002 percent to 0.2 percent by weight.
 5. The process as claimed in claim 1 in which the peroxide is hydrogen peroxide.
 6. The process as claimed in claim 1 in which the aqueous solution contains an alcohol to prevent solubilization of the oxidized cellulose.
 7. The process as claimed in claim 1 which includes the step of subjecting the oxidized cellulosic material to a reduction reaction prior to the mild oxidation step.
 8. The process as claimed in claim 7 in which the reduction reaction is carried out in the presence of a borohydride selected from the group consisting of an alkali metal borohydride and an alkaline earth metal borohydride.
 9. The process as claimed in claim 7 in which the reduction is carried out in the presence of nascent hydrogen.
 10. In the process for preparing a smoking product from cellulosic material in which the cellulosic material has previously been oxidized with nitrogen dioxide, the step of subjecting the oxidized cellulose to a mild oxidation by wetting the oxidized cellulosic material with aqueous medium and exposing the wet oxidized cellulosic material to ozone.
 11. A smoking product formed of cellulosic material oxidized with nitrogen dioxide and subjected to a subsequent mild oxidation with a peroxide selected from the group consIsting of hydrogen peroxide and an alkali metal peroxide, as described in claim
 1. 